That is great that you lift weights and also use the punching bag. I wish I had done that at your age. You are taking initiative. That alone will benefit you in the future. Keep going.
I don't have a punching bag, but have thought about getting one. Do you have one that hangs from the ceiling or is free standing? I saw a travel punching bag you can hook up to a door frame. What do you like or don't like about your punching bag?
I actually bought a reflex ball. You wear a headband, which has a string. There is a ball at the end of the string and you punch it before it hits you in the face. It's very difficult and I doubt it's much exercise. I don't do it very much, but it's fun sometimes.
That is great that you are drinking less soda and not eating potato chips. Regarding the soda, it's good to get into the habit of politely saying "No thank you" even if everyone else is drinking it. It can feel awkward at first, but you can politely ask for water. Everyone has water available for guests. I think it's best to give up the soda and don't look back. Besides causing weight gain, it's also very bad for your teeth. I used to get a lot of cavities when I drank soda.
Regarding sugar free peanut butter, I am not sure. I eat Crazy Richard's peanut butter. The only ingredient is peanuts. It has to be mixed before you use it. There are special mixer lids you can buy to make it easier. I think crunchy tastes better than smooth. I am not trying to lose weight, so I don't know what advice to give about if this is good peanut butter for you. Perhaps other could chime in. Of course it depends on how much of it you eat.
Keep going man. You will learn so much by doing this at such a young age. You will look back one day and be so glad you did. Always free to post if you get frustrated and people here will support you.